National Assessment of Geologic Carbon Dioxide Storage 

Resources—Data

U.S. Department of the Interior

U.S. Geological Survey

Data Series 774

Version 1.1, September 2013

120°W 110°W 100°W 90°W 80°W 70°W

40°N

30°N

160°W 140°W

65°N

60°N

55°N

180°W

Evaluated area

Assessed area

EXPLANATION 0 250 500 750 1,000KILOMETERS

0 250 500 MILES 0 250 500 KILOMETERS

0 250 MILES

Pacific

Northwest

Rocky Mountains

and Northern

Great Plains

Western

Mid-Continent Eastern Mesozoic Rift Basins

Eastern Mid-Continent

Coastal Plains

Alaska

California

Bighorn Basin

Powder

River

Basin

Wind River Basin

Greater Green

River Basin

Hanna, 

Laramie, and 

Shirley Basins

Western

Oregon and Washington

Basins

Columbia Basin of 

Oregon, Washington, 

and Idaho

Wyoming–Idaho–Utah 

Thrust Belt

Alaska 

North Slope

Kandik 

Basin

U.S. Gulf Coast Bend Arch

and Fort

Worth Basin

Arkoma Basin

Denver 

Basin

Anadarko and Southern 

Oklahoma Basins

Eastern 

Great 

Basin

Sacramento

Basin

San 

Joaquin 

Central Basin California 

Coast Basins

Ventura 

Basin

Los Angeles 

Basin

Uinta and Piceance Basins

Paradox 

Basin

San Juan

Basin

Raton 

Basin

Williston 

Basin

Illinois 

Basin

Michigan 

Basin

South Florida 

Basin

Black 

Warrior 

Basin

Appalachian 

Basin

Kansas 

Basins

Palo Duro 

Basin

Permian Basin

Eastern 

Mesozoic 

Rift Basins

Atlantic 

Coastal Plain

Base map from Jarvis

and others (2008)

CGIAR-Consortium

for Spatial Information

SRTM 90m Database
Cover. Map of the conterminous United States and Alaska showing 8 regions (separated by bold 

dashed lines and labeled in a bold font), evaluated areas (bluish gray) that were not assessed, and 

36 areas (pattern) that were assessed by the U.S. Geological Survey for carbon dioxide storage. The 

assessed areas contain multiple storage assessment units.
National Assessment of Geologic 

Carbon Dioxide Storage Resources—

Data

By U.S. Geological Survey Geologic Carbon Dioxide Storage Resources 

Assessment Team

Data Series 774

Version 1.1, September 2013

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

Version 1.0 was released June 26, 2013

Version 1.1 was released September 2013

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Suggested citation:

U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team, 2013, National assessment 

of geologic carbon dioxide storage resources—Data (ver. 1.1, September 2013): U.S. Geological Survey Data Series 

774, 13 p., plus 2 appendixes and 2 large tables in separate files, http://pubs.usgs.gov/ds/774/. (Supersedes ver. 1.0 

released June 26, 2013.)
iii

Members of the U.S. Geological Survey 

Geologic Carbon Dioxide Storage Resources 

Assessment Team1

Peter D. Warwick, Project Chief

Madalyn S. Blondes

Sean T. Brennan

Marc L. Buursink

Steven M. Cahan

James L. Coleman

Troy A. Cook

Margo D. Corum

Jacob A. Covault

William H. Craddock

Christina A. DeVera

Colin Doolan

Ronald M. Drake II

Lawrence J. Drew

Joseph A. East

Philip A. Freeman

Christopher P. Garrity

Kevin J. Gooley

Mayur A. Gosai

Hossein Jahediesfanjani2

Celeste D. Lohr

John C. Mars

Matthew D. Merrill

Ricardo A. Olea

Tina L. Roberts-Ashby

William A. Rouse

Paul G. Schruben

John H. Schuenemeyer2

Ernie R. Slucher

Brian A. Varela

Mahendra K. Verma

1

All members are or were with the U.S. Geological Survey unless otherwise indicated.

2

Contractor.

v

Contents

Members of the U.S. Geological Survey Geologic Carbon Dioxide Storage Resources 

Assessment Team ...........................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Description of the Storage Assessment Unit Input Data Form ..............................................................1

Description of the Empirical Cumulative Distribution Function Plots ...................................................2

Description of the Comprehensive Data Table .........................................................................................3

Description of the Correlation Matrix for Aggregation ...........................................................................3

Data Sources..................................................................................................................................................3

Acknowledgments.........................................................................................................................................6

References Cited............................................................................................................................................6

Glossary...........................................................................................................................................................8

Appendix 1. Input Data Forms for 192 Storage Assessment Units 

Used in the U.S. Geological Survey National Assessment 

of Geologic Carbon Dioxide Storage Resources......................Available as a separate file

Appendix 2. Empirical Cumulative Distribution Function Plots 

of Six Resource Types for Each of the 192 Storage 

Assessment Units Used in the U.S. Geological Survey 

National Assessment of Geologic Carbon Dioxide 

Storage Resources........................................................................Available as a separate file

Figure

1. Input data form used for each storage assessment unit 

(SAU) that was analyzed quantitatively during the 

U.S. Geological Survey national assessment of 

geologic carbon dioxide (CO2) storage resources ..................................................................4

Tables

1. Comprehensive presentation of data used in the 

U.S. Geological Survey national assessment of 

geologic carbon dioxide storage resources .............................Available as a separate file

2. Correlation matrix for aggregation of data used in the 

U.S. Geological Survey national assessment of 

geologic carbon dioxide storage resources .............................Available as a separate file
vi

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

mile, nautical (nmi) 1.852 kilometer (km)

meter (m) 3.281 foot (ft)

Area

square inch (in2

) 6.452 square centimeter (cm2)

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2

)

Volume

gallon (gal) 3.785 liter (L)

barrel (bbl) (petroleum, 1 barrel = 

42 gal)

0.1590 cubic meter (m3

)

cubic foot (ft3

) 0.02832 cubic meter (m3)

liter (L) 0.2642 gallon (gal)

cubic meter (m3

) 6.290 barrel (petroleum, 1 barrel = 

42 gal)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg)

ton, short (2,000 lb) 0.9072 megagram (Mg)

ton, long (2,240 lb) 1.016 megagram (Mg)

milligram (mg) 0.00003527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (lb)

megagram (Mg) = 1 metric ton (t) 

(1,000 kg)

1.102 ton, short (2,000 lb)

megagram (Mg) 0.9842 ton, long (2,240 lb)

megaton (Mt) = 1 million metric tons 1.102 million short tons

gigaton (Gt) = 1 billion metric tons 1.102 billion short tons

Pressure

bar 100 kilopascal (kPa)

pound-force per square inch 

(lbf/in2

 or psi)

6.895 kilopascal (kPa)

kilopascal (kPa) 0.01 bar

kilopascal (kPa) 0.1450 pound-force per square inch 

(lbf/in2

)

Pressure gradient

pound-force per square inch per foot 

(lbf/in2

/ft or psi/ft)

22.62 kilopascal per meter (kPa/m)

Density

kilogram per cubic meter (kg/m3

) 0.06242 pound per cubic foot (lb/ft3)

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L).

Permeability is given in darcies (D) and millidarcies (mD).

1 barrel of oil equivalent (BOE) = 1 barrel of crude oil (42 gallons)

 = 6,000 cubic feet of natural gas

 = 1.5 barrels of natural gas liquids
vii

Abbreviations, Acronyms, and Symbols

ASF area of the storage formation within the storage assessment unit

AU assessment unit, part of the USGS National Oil and Gas Assessment

BPV buoyant trapping pore volume

BSE buoyant trapping storage efficiency

BSR buoyant trapping storage resource

BSV buoyant trapping storage volume

bbl petroleum barrel or barrels

BLM Bureau of Land Management

BOE barrel of oil equivalent; see glossary

BOEM Bureau of Ocean Energy Management

CDF cumulative distribution function

CO2 carbon dioxide

COTSA CO2 Sequestration Assessment program

D darcy

FVF formation volume factor

FVFgas formation volume factor for gas

FVFNGL formation volume factor for natural gas liquids

FVFoil formation volume factor for oil

GOR gas:oil ratio

Gt gigaton = billion metric tons

k permeability

KR known recovery production and reserve volumes

KRRES known recovery production volumes converted to reservoir conditions

KRRSR known recovery replacement storage resource

mD millidarcy

MMbbl million petroleum barrels

Mt megaton = million metric tons

NCRDS USGS National Coal Resources Data System

NETL National Energy Technology Laboratory

NGL natural gas liquids

NOGA USGS National Oil and Gas Assessment
viii

P5 probability percentile—5-percent probability that the true value is less than the 

given value

P50 probability percentile—50-percent probability that the true value is less than the 

given value. P50 is the median of the probability distribution.

P95 probability percentile—95-percent probability that the true value is less than the 

given value

psi pound-force per square inch

Rk permeability distribution

RW the area fraction of the SAU available for storage after consideration of EPA waterquality guidelines or highly fractured seals

R1PV residual trapping class 1 pore volume

R1SE residual trapping class 1 storage efficiency

R1SR residual trapping class 1 storage resource

R1SV residual trapping class 1 storage volume

R2PV residual trapping class 2 pore volume

R2SE residual trapping class 2 storage efficiency

R2SR residual trapping class 2 storage resource

R2SV residual trapping class 2 storage volume

R3PV residual trapping class 3 pore volume

R3SE residual trapping class 3 storage efficiency

R3SR residual trapping class 3 storage resource

R3SV residual trapping class 3 storage volume

RCSP Regional Carbon Sequestration Partnership

SAU storage assessment unit

SE storage efficiency

SF storage formation

SFPV storage formation pore volume

TPI thickness of the net porous interval

TASR technically accessible storage resource

TASV technically accessible storage volume

TDS total dissolved solids

USGS U.S. Geological Survey

Z factor critical value: standard deviations from the mean for a given probability assumption

CO 2 density of carbon dioxide

 porosity

 PI porosity of the net porous interval
National Assessment of Geologic Carbon Dioxide Storage 

Resources—Data

By U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team

Abstract

In 2012, the U.S. Geological Survey (USGS) completed 

the national assessment of geologic carbon dioxide storage 

resources. Its data and results are reported in three publications: the assessment data publication (this report), the assessment results publication (U.S. Geological Survey Geologic 

Carbon Dioxide Storage Resources Assessment Team, 2013a, 

USGS Circular 1386), and the assessment summary publication (U.S. Geological Survey Geologic Carbon Dioxide 

Storage Resources Assessment Team, 2013b, USGS Fact 

Sheet 2013–3020). This data publication supports the results 

publication and contains (1) individual storage assessment unit 

(SAU) input data forms with all input parameters and details 

on the allocation of the SAU surface land area by State and 

general land-ownership category; (2) figures representing the 

distribution of all storage classes for each SAU; (3) a table 

containing most input data and assessment result values for 

each SAU; and (4) a pairwise correlation matrix specifying 

geological and methodological dependencies between SAUs 

that are needed for aggregation of results.

Introduction

In 2012, the U.S. Geological Survey (USGS) completed 

the national assessment of geologic carbon dioxide storage 

resources, hereinafter called the assessment. Its data and 

results are reported in three publications: the assessment data 

publication (this report), the assessment results publication 

(U.S. Geological Survey Geologic Carbon Dioxide Storage 

Resources Assessment Team, 2013a), and the assessment summary publication (U.S. Geological Survey Geologic Carbon 

Dioxide Storage Resources Assessment Team, 2013b). This 

data publication supports the results publication and contains 

(1) an input data form for each storage assessment unit (SAU) 

that was analyzed quantitatively (appendix 1), (2) empirical 

cumulative distribution function (CDF) plots of assessment 

results for each SAU (appendix 2), (3) a table containing most 

inputs to and outputs from the assessment (table 1), and (4) a 

correlation matrix for aggregation (table 2). These components 

are not in the results or summary publications cited above.

This data publication and the companion results report 

and summary report (U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team, 2013a,b) 

are parts of a suite of USGS reports that document the development of the assessment methodology and the execution 

and reporting of the assessment. The assessment methodology described by Burruss and others (2009) and Brennan and 

others (2010) was modified slightly during the assessment, as 

summarized in the implementation report by Blondes, Brennan, and others (2013). Geologic descriptions of the SAUs 

in basins or combined basin areas were prepared during the 

assessment, and some have been released as chapters of a 

report edited by Warwick and Corum (2012).

Description of the Storage Assessment 

Unit Input Data Form

This section explains the 192 SAU input data forms in 

appendix 1 that were completed for the national assessment. 

The SAU is a mappable volume of rock that consists of a 

porous reservoir and a bounding regional sealing formation 

(Brennan and others, 2010). Within the SAU, the porous 

reservoir is defined as the storage formation (SF). Sedimentary 

rocks of deep saline formations and of existing oil and gas 

fields were evaluated. Specifically, 36 sedimentary basins, or 

combined basin areas, within 8 regions of the conterminous 

United States and Alaska were assessed. Within the assessed 

basins, 202 SAUs were identified as having good storage 

potential because of the presence of a robust regional seal, 

adequate reservoir rock, and sufficient areas containing saline 

formation waters. Ten of these SAUs did not have sufficient 

data to build a robust geologic model to accurately estimate 

the storage resource and were designated as nonquantitative SAUs. No storage resources were estimated for the 10 

nonquantitative SAUs, and input forms were not prepared 

for them. Three basins (Central California Coast Basins; 

Columbia Basin of Oregon, Washington, and Idaho; and Raton 

Basin) contain only nonquantitative SAUs and are included in 

table 1 but not in the correlation matrix (table 2). For nonquantitative SAUs, surficial geographic boundaries were defined 

and a geologic description was prepared.
2 National Assessment of Geologic Carbon Dioxide Storage Resources—Data

The USGS assessed the technically accessible storage 

resources (TASR) for carbon dioxide (CO2) in geologic formations underlying the onshore area and State waters area of the 

United States; resources in federally owned offshore areas 

were not assessed because resource assessments in these areas 

are typically done by the Bureau of Ocean Energy Management (BOEM). Federally owned offshore areas generally 

extend from 3 or more geographic (nautical) miles from the 

established baseline for the coast to an outer limit of 200 

geographic miles. The offshore areas on the input form are 

defined as State waters, or those submerged areas between 

the established baseline for the coast and the federally owned 

offshore areas.

All assessments were conducted by USGS employees 

to ensure the use of a consistent process and to avoid outside 

influence. A permanent panel of experienced assessment 

geologists presided over all assessment meetings and worked 

with the assessment geologist to arrive at a consensus for the 

values entered on the input data forms.

The first page of the input form (fig. 1) contains identification information and the assessment geologist’s inputs; 

the second page contains allocation percentages of the SAU 

mean area to the States that are listed alphabetically and of 

the SAU area to five general land-ownership categories that 

are defined in the “Glossary” in this report: Federal lands, 

State lands, Tribal lands, private and other lands, and offshore 

areas. Each input form is identified with an SAU name and 

a unique SAU code number following the style established 

by the USGS National Oil and Gas Assessment (NOGA) 

publications, as explained by Blondes, Brennan, and others 

(2013) and the “Glossary” in this report. A list of SAU names 

and codes by basin is in table 1. In addition to identifying the 

SAU, the input form contains spaces for the assessment geologist’s name, the date of assessment, and the SAU location and 

its relation to NOGA assessment units (AUs), if appropriate, 

along with any notes from the assessor. In the input forms in 

appendix 1, no entries are shown for the last two categories 

because the information about the NOGA AUs was lengthy 

for some SAUs and because there were no significant notes 

from the assessors. Information on the related NOGA AUs is 

in table 1.

The first page of the input data form has spaces for the 

geologist to indicate whether the SAU consists of formations between depths of 3,000 and 13,000 feet (9l4 and 3,962 

meters) or of formations more than 13,000 feet below the 

ground surface (fig. 1). These depths distinguish a standard 

SAU from a deep SAU. Lines 1–9 contain depth information 

and input parameters for each SAU that were used to probabilistically calculate storage resources.

These input values in lines 1–9 are typically the minimum, most likely, and maximum estimates made by the 

assessment geologist with the help of the assessment panel for 

the following parameters:

Line 1: SAU depth from surface in feet

Line 2: Area of the SAU in acres

Line 3: Mean total SAU thickness in feet

Line 4: Likely SAU water quality in terms of salinity greater than or less than 10,000 milligrams 

per liter of total dissolved solids (mg/L TDS) 

as described in Blondes, Brennan, and others 

(2013)

Line 5: Area fraction available for storage (Blondes, 

Brennan, and others, 2013)

Line 6: Mean thickness of the net porous interval in feet

Line 7: Mean porosity of the net porous interval as a 

fraction

Line 8: Buoyant trapping pore volume in millions of 

barrels (MMbbl)

Line 9: Permeability of the net porous interval in 

millidarcies, which is used in estimating residual 

trapping storage characteristics

The second page of the input data form has allocations 

of the SAU mean area to the States that it underlies and to 

general land-ownership categories (fig. 1). A cartographer calculated the percentage of each SAU’s mean area for each State 

and land-ownership category. Although volume allocations 

are commonly completed for basin-specific AUs in the USGS 

NOGA, time and data constraints for this assessment of CO2

storage precluded this type of allocation for SAUs. Acronyms 

and abbreviations reduce the length of the assessment input 

forms; their definitions can be found in the “Abbreviations, 

Acronyms, and Symbols” section at the beginning of this document or the “Glossary” section at the end of this document.

Description of the Empirical 

Cumulative Distribution Function Plots

This section explains the empirical cumulative distribution function (CDF) plots in appendix 2 for the storage 

resources. The empirical CDF plots in appendix 2 are arranged 

alphabetically by basin name and then numerically by SAU 

code. A complete list of basin names, SAU names, and 

SAU codes is in table 1. Each page in appendix 2 shows the 

probabilistic results of one quantitatively assessed SAU and 

contains six plots, one for each assessment output. These outputs are (1) the technically accessible storage resource (TASR); 

(2) the buoyant trapping storage resource (BSR); (3) the known 

recovery replacement storage resource (KRRSR); (4) the residual trapping class 1 storage resource (R1SR), for rocks with 

permeability greater than 1 darcy (D); (5) the residual trapping 

class 2 storage resource (R2SR), for rocks with permeability 

between 1 millidarcy (mD) and 1 D; and (6) the residual trapping class 3 storage resource (R3SR), for rocks with permeability less than 1 mD. In each CDF plot, the horizontal axis 

shows the storage resource (in millions of metric tons, Mt) and 
Data Sources 3

the vertical axis shows the cumulative probability between 

zero and one. The cumulative probability for a given percentile represents the probability that the true storage resource is 

less than the value shown. The points along the CDF are the 

mean and the P5, P50, and P95 percentiles. These values are also 

given in table 1. Output categories with a calculated storage 

resource of zero are labeled “No storage resource.” For more 

details on the calculations used to create the empirical CDF 

plots, see Brennan and others (2010) and Blondes, Brennan, 

and others (2013).

Description of the Comprehensive Data 

Table

This section explains the comprehensive data presentation in table 1, which lists most inputs necessary to replicate 

the assessment team’s probabilistic resource calculations for 

individual quantitative SAUs. Table 1 includes inputs from 

the input data forms; basin-scale parameters such as formation volume factors, storage efficiencies, and CO2

 densities; 

Z factors used to calculate lognormal distributions for permeability and buoyant trapping pore volume (Blondes, Brennan, 

and others, 2013); six assessment outputs as storage resources; 

and general assessment information such as the name of the 

assessment geologist, the date of assessment, SAU names, 

and SAU codes. To calculate the aggregated basin, region, and 

national storage resources, it is necessary to use the correlation 

matrix in table 2 for aggregation (Blondes, Brennan, and others, 2013; Blondes, Schuenemeyer, and others, 2013).

Description of the Correlation Matrix 

for Aggregation

The assessment uses a probabilistic addition, or aggregation, methodology (Blondes, Brennan, and others, 2013; 

Blondes, Schuenemeyer, and others, 2013) to correctly 

propagate uncertainty when combining SAU resources to a 

basin, regional, or national scale. The probabilistic aggregation 

methodology requires two main inputs: (1) stochastic storage 

resource estimates for each SAU, represented by the empirical CDFs described above, and (2) a pairwise correlation 

matrix specifying geological and methodological dependencies between SAUs. The correlation matrix for aggregation 

(table 2) contains matching column and row titles showing the 

region name, basin name, SAU name, and SAU code. The column and row intersection within the correlation matrix of two 

SAUs represents the correlation coefficient for that SAU pair. 

Note that the coefficient along the diagonal is always one. The 

SAUs are grouped by region and basin and are listed numerically by code in table 2.

Data Sources

Assessment geologists used geologic data from sources 

including USGS (published and unpublished) reports and 

maps, published literature such as journal articles and 

textbooks, and research-consortium-funded Web sites. 

Examples of USGS sources include previous NOGA publications (http://energy.usgs.gov/OilGas/AssessmentsData/

NationalOilGasAssessment.aspx), the National Geologic 

Map Database (http://ngmdb.usgs.gov/ngmdb/ngmdb_home.

html), the Geologic Names Lexicon (http://ngmdb.usgs.gov/

Geolex/), and the Publications Warehouse database (http://

pubs.er.usgs.gov/). Water-quality data were obtained from 

many sources, including the USGS produced-waters database 

(Breit, 2002), various regional compilations (for example, 

Blondes and Gosai, 2011), the National Energy Technology 

Laboratory (NETL) Brine Database (Hovorka and others, 

2000), and datasets available from State sources.

Additional data were obtained from cooperative agreements such as the CO2

 Sequestration Assessment (COTSA) 

program through the National Coal Resources Data System 

(NCRDS), which funded 35 State agencies to provide highquality geologic information, and data-sharing agreements 

with the NETL Regional Carbon Sequestration Partnerships 

(RCSP). These agreements provided formal interpretive 

publications and summary reports, as well as unpublished data 

containing, for example, depth-to-top-of-formation interpretations from drilling; subsurface pressure, temperature, porosity, 

and permeability ranges; and thickness of the porous interval 

and the ratio of porous thickness to total thickness (also known 

as net-to-gross) estimates.

Assessment geologists used several proprietary databases 

to support their interpretations. The “Significant Oil and Gas 

Fields of the United States Database” from Nehring Associates, Inc. (2010), provided quantitative field- and reservoirlevel data (current as of December 2008). It includes reservoir 

porosity, permeability, temperature, and pressure and hydrocarbon production data such as reserves, cumulative production, and various other types of information for most oil and 

gas fields and reservoirs containing more than 0.5 million 

barrels of oil equivalent (BOE). The Petroleum Information 

Data Model (PIDM) well relational database (IHS Inc., 2010) 

served as a source for depth-to-top-of-formation interpretations, bottom-hole temperatures, and estimated reservoir 

cumulative production and prorated cumulative production 

in States where the Nehring database provided production 

and reserve estimates only at the field level. The Web-based 

Enerdeq database (IHS Inc., 2011a) contains comprehensive 

well attribute sets with formation penetration data, from 

which drilling density estimates are derived. These databases were also used to find and identify well logs, estimate 

drilled intervals, find perforation intervals, and locate porosity 

and permeability data. Assessment geologists used the IHS 

Interpreted Formation Tops and Online Structure Maps (IHS 

Inc., 2011b) where possible; the data were current as of 2011. 
4 National Assessment of Geologic Carbon Dioxide Storage Resources—Data

Assessment geologist: Date:

Assessment region:

Province: Number:

Basin: Number:

Storage Assessment Unit (SAU): Number:

SAU relationship to NOGA AU:

Notes from assessor: 

Lines 1-9 concern data for the SAU at depths of (check one): 3,000-13,000 ft

> 13,000 ft

(1) SAU depth from surface (ft): minimum: most likely: maximum:

(2) Area of the SAU (acres): minimum: most likely: maximum:

(3) Mean total SAU thickness (ft): minimum: most likely: maximum:

(4) SAU water quality (check one):

Most of the water in the SAU is saline (greater than 10,000 mg/L TDS).

Water in this SAU is both saline and fresh.

Most of the water in the SAU is fresh (less than 10,000 mg/L TDS).

(5) Area fraction available for storage (generally, the area where SAU pore water has more than 10,000 mg/L TDS):

minimum: most likely: maximum:

(6) Mean thickness net porous interval (ft): minimum: most likely: maximum:

(7) Mean porosity net porous interval (fraction): minimum: most likely: maximum:

(8) Buoyant trapping pore volume (MMbbl):

minimum: most likely: maximum:

(9) Permeability of the net porous interval (mD): minimum: most likely: maximum:

Characteristics of the Storage Assessment Unit

Buoyant Trapping Probabilistic Calculation Inputs

Residual Trapping Probabilistic Calculation Inputs

STORAGE ASSESSMENT UNIT INPUT DATA FORM

Identification Information
Data Sources 5

Storage Assessment Unit (SAU): Number:

(1) contains % of mean SAU area

(2) contains % of mean SAU area

(3) contains % of mean SAU area

(4) contains % of mean SAU area

(5) contains % of mean SAU area

(6) contains % of mean SAU area

(7) contains % of mean SAU area

(8) contains % of mean SAU area

(1) Federal lands contain % of mean SAU area

(2) State lands contain % of mean SAU area

(3) Tribal lands contain % of mean SAU area

(4) Private and other lands contain % of mean SAU area

(5) Offshore areas contain % of mean SAU area

Allocations of the SAU to States

Allocations of the SAU to General Land-Ownership Categories

Figure 1 (facing page and above). Input data form used 

for each storage assessment unit (SAU) that was analyzed 

quantitatively during the U.S. Geological Survey national 

assessment of geologic carbon dioxide (CO2) storage resources. 

These data inputs were used in the calculations described in 

Brennan and others (2010) and Blondes, Brennan, and others 

(2013). Some of the data inputs are solely descriptive and were 

not used in the calculations (for example, lines 1, 3, and 4 on the 

first page), although they were helpful in determining other data 

input parameters. Completed data forms for the 192 quantitative 

SAUs are in appendix 1; they are arranged alphabetically by 

basin name and then numerically by SAU code.
6 National Assessment of Geologic Carbon Dioxide Storage Resources—Data

Carbon dioxide storage resources were allocated to States and 

land-ownership categories by using State-specific geospatial 

data primarily from the Bureau of Land Management (BLM) 

(http://www.blm.gov) and secondarily from either individual 

State agencies or the National Atlas of the United States®

(http://nationalatlas.gov/).

Acknowledgments

The U.S. Geological Survey Geologic Carbon Dioxide 

Storage Resources Assessment Team acknowledges the helpful reviews of this report by Kevin Jones and Michael Trippi 

of the USGS. Additional acknowledgements for the assessment process are included in the assessment results publication 

(U.S. Geological Survey Geologic Carbon Dioxide Storage 

Resources Assessment Team, 2013a).

References Cited

Bachu, Stefan, 2003, Screening and ranking of sedimentary 

basins for sequestration of CO2 in geological media in 

response to climate change: Environmental Geology, v. 44, 

p. 277–289.

Blondes, M.S., Brennan, S.T., Merrill, M.D., Buursink, M.L., 

Warwick, P.D., Cahan, S.M., Cook, T.A., Corum, M.D., 

Craddock, W.H., DeVera, C.A., Drake, R.M., II, Drew, L.J., 

Freeman, P.A., Lohr, C.D., Olea, R.A., Roberts-Ashby, T.L., 

Slucher, E.R., and Varela, B.A., 2013, National assessment 

of geologic carbon dioxide storage resources—Methodology implementation: U.S. Geological Survey Open-File 

Report 2013–1055, 26 p., accessed May 10, 2013 at http://

pubs.usgs.gov/of/2013/1055/.

Blondes, M.S., and Gosai, M.A., 2011, An expanded Wyoming water quality database [abs.]: American Association of Petroleum Geologists Rocky Mountain Section, 

Annual Meeting, Cheyenne, Wyo., June 25–29, 2011, 

Abstracts, 1 p., accessed March 10, 2013, at http://www.

searchanddiscovery.com/abstracts/pdf/2011/rocky/abstracts/

ndx_blondes.pdf.

Blondes, M.S., Schuenemeyer, J.H., Olea, R.A., and Drew, 

L.J., 2013, Aggregation of carbon dioxide sequestration storage assessment units: Stochastic Environmental 

Research and Risk Assessment, DOI:10.1007/s00477-

013-0718-x, 21 p., accessed May 31, 2013, at http://link.

springer.com/article/10.1007%2Fs00477-013-0718-x.

Breit, G.N., comp., 2002, Produced waters database: U.S. 

Geological Survey database, accessed January 19, 2011, at 

http://energy.cr.usgs.gov/prov/prodwat/.

Brennan, S.T., Burruss, R.C., Merrill, M.D., Freeman, P.A., 

and Ruppert, L.F., 2010, A probabilistic assessment methodology for the evaluation of geologic carbon dioxide storage: 

U.S. Geological Survey Open-File Report 2010–1127, 31 

p., accessed September 19, 2012, at http://pubs.usgs.gov/

of/2010/1127.

Burruss, R.C., Brennan, S.T., Freeman, P.A., Merrill, M.D., 

Ruppert, L.F., Becker, M.F., Herkelrath, W.N., Kharaka, 

Y.K., Neuzil, C.E., Swanson, S.M., Cook, T.A., Klett, T.R., 

Nelson, P.H., and Schenk, C.J., 2009, Development of a 

probabilistic assessment methodology for evaluation of 

carbon dioxide storage: U.S. Geological Survey Open-File 

Report 2009–1035, 81 p., accessed September 19, 2012, at 

http://pubs.usgs.gov/of/2009/1035/.

Everitt, B.S., and Skrondal, Anders, 2010, The Cambridge 

dictionary of statistics (4th ed.): Cambridge, England, Cambridge University Press, 478 p.

Hovorka, S.D., Romero, M.L., Treviño, R.H., Warne, A.G., 

Ambrose, W.A., Knox, P.R., and Tremblay, T.A., 2000, 

Project evaluation, Phase II; Optimal geological environments for carbon dioxide disposal in brine-bearing formations (aquifers) in the United States: The University of 

Texas at Austin, Bureau of Economic Geology, final report 

prepared for U.S. Department of Energy, National Energy 

Technology Laboratory, under contract no. DE–AC26–

98FT40417, 232 p. (GCCC [Gulf Coast Carbon Center] 

Digital Publication Series 00–01, available at http://www.

beg.utexas.edu/gccc/bookshelf/Final%20Papers/00-01-

Final.pdf.)

IHS Inc., 2010, PIDM [Petroleum Information Data Model] 

relational U.S. well data [data current as of December 23, 

2009]: Englewood, Colo., IHS Inc., database.

IHS Inc., 2011a, Enerdeq U.S. well data: Englewood, Colo., 

IHS Inc., database, accessed January 20, 2011, at http://

energy.ihs.com/.

IHS Inc., 2011b, IHS interpreted formation tops and online 

structure maps [data current as of 2011]: Englewood, Colo., 

IHS Inc., database.

Jarvis, A., Reuter, H.I., Nelson, Andrew, and Guevara, 

Edward, 2008, Hole-filled SRTM [Shuttle Radar Topographic Mission] for the globe, version 4: available from 

the CGIAR [Consultative Group for International Agricultural Research]-Consortium for Spatial Information SRTM 

90m Database; accessed January 15, 2012, at http://www.

cgiar-csi.org/data/srtm-90m-digital-elevation-database-v4-

1#acknowledgements.

Klett, T.R., Schmoker, J.W., Charpentier, R.R., Ahlbrandt, 

T.S., and Ulmishek, G.F., 2005, Glossary, chap. 25 of
References Cited 7

U.S. Geological Survey Southwestern Wyoming Province 

Assessment Team, Petroleum systems and geologic assessment of oil and gas in the Southwestern Wyoming Province, 

Wyoming, Colorado, and Utah: U.S. Geological Survey 

Digital Data Series DDS–69–D, 3 p., on CD-ROM. (Also 

available at http://pubs.usgs.gov/dds/dds-069/dds-069-d/.)

MacMinn, C.W., Szulczewski, M.L., and Juanes, Ruben, 2010, 

CO2 migration in saline aquifers. Part 1, Capillary trapping under slope and groundwater flow: Journal of Fluid 

Mechanics, v. 662, p. 329–351.

Nehring Associates, Inc., 2010, Significant oil and gas fields 

of the United States database [data current as of December 

2008]: Colorado Springs, Colo., Nehring Associates, Inc.

R Core Team, 2013, R—A language and environment for 

statistical computing (version 3.0.0): Vienna, Austria, R 

Foundation for Statistical Computing, http://www.R-project.

org/.

Schlumberger, 2011, Injectivity test, [entry] in Schlumberger 

oilfield glossary: Schlumberger Web site, accessed December 20, 2012, at http://www.glossary.oilfield.slb.com/

Display.cfm?Term=injectivity%20test.

Schmoker, J.W., and Klett, T.R., 2005, U.S. Geological Survey 

assessment concepts for conventional petroleum accumulations, chap. 19 of U.S. Geological Survey Southwestern 

Wyoming Province Assessment Team, Petroleum systems 

and geologic assessment of oil and gas in the Southwestern 

Wyoming Province, Wyoming, Colorado, and Utah: U.S. 

Geological Survey Digital Data Series, DDS–69–D, 6 p., 

accessed February 20, 2013, at http://pubs.usgs.gov/dds/

dds-069/dds-069-d/REPORTS/69_D_CH_19.pdf.

Thormahlen, L.F., 1999, Boundary development on the outer 

continental shelf: Minerals Management Service Mapping 

and Boundary Branch, OCS report MMS 99–0006, 12 

p., accessed February 21, 2013, at http://www.boem.gov/

BOEM-Newsroom/Library/Publications/1999/99-0006-pdf.

aspx.

U.S. Geological Survey Geologic Carbon Dioxide Storage 

Resources Assessment Team, 2013a, National assessment 

of geologic carbon dioxide storage resources—Results (ver. 

1.1, September 2013): U.S. Geological Survey Circular 

1386, 41 p., http://pubs.usgs.gov/circ/1386/. (Supersedes 

ver. 1.0 released June 26, 2013.)

U.S. Geological Survey Geologic Carbon Dioxide Storage 

Resources Assessment Team, 2013b, National assessment 

of geologic carbon dioxide storage resources—Summary 

(ver. 1.1, September 2013): U.S. Geological Survey Fact 

Sheet 2013–3020, 6 p., http://pubs.usgs.gov/fs/2013/3020/. 

(Supersedes ver. 1.0 released June 26, 2013.)

Warwick, P.D., and Corum, M.D., eds., 2012, Geologic framework for the national assessment of carbon dioxide storage resources: U.S. Geological Survey Open-File Report 

2012–1024, accessed February 21, 2013, at http://pubs.usgs.

gov/of/2012/1024/. (Chapters A–C were posted by November 1, 2012.)

Wickham, Hadley, 2009, ggplot2; Elegant graphics for data 

analysis: New York, Springer, 221 p.
8 National Assessment of Geologic Carbon Dioxide Storage Resources—Data

Glossary

at http://www.blm.gov and the National Atlas of the United 

States® at http://nationalatlas.gov/mld/fedlanp.html.

federally owned offshore areas Federal jurisdiction begins 

at 3 geographic (nautical) miles from the established baseline 

for the coast and extends to an outer limit of 200 nautical 

miles. However, there are special cases. Because of claims 

existing at the dates of statehood, Texas and the Gulf Coast of 

Florida have proprietary interest in a submerged belt of land, 

9 geographic miles wide, extending seaward along the coast 

(Thormahlen, 1999). Resource assessments in federally owned 

offshore areas are typically done by the Bureau of Ocean 

Energy Management (BOEM).

gas:oil ratio (GOR) Ratio of gas to oil (in cubic feet per 

barrel) in a hydrocarbon accumulation. GOR is calculated by 

using volumes of gas and oil at surface conditions.

gas reservoir A subsurface accumulation of hydrocarbons 

primarily in the gas phase that is contained in porous or 

fractured rock formations. A gas accumulation is defined by 

the USGS (Klett and others, 2005) as having a gas:oil ratio of 

20,000 cubic feet per barrel or greater.

geologic storage of CO2 A type of carbon sequestration that 

utilizes the long-term retention of carbon dioxide in subsurface 

geologic formations.

injectivity The “Schlumberger Oilfield Glossary” (Schlumberger, 2011) defines an injectivity test as a procedure that is 

used to determine “the rate and pressure at which fluids can be 

pumped into the treatment target without fracturing the formation.” Although injectivity is typically reported as a rate, the 

methodology used in this assessment addresses this requirement by using permeability values to divide the residual 

storage component of the storage formation into three classes; 

see residual trapping classes 1, 2, and 3. The permeability is a 

proxy for injectivity because actual CO2 injection rate data are 

generally limited to enhanced-oil-recovery operations using 

CO2 and are not available for various reservoir types.

known recovery production volumes The cumulative petroleum production and proved reserves for a given reservoir.

known recovery replacement storage resource (KRRSR) The 

storage resource calculated from known recovery production 

volumes.

minimum size The lower limit for inclusion of oil and gas 

field information in assessment calculations. Following USGS 

oil and gas assessment methodology (Schmoker and Klett, 

2005), volumetric data from accumulations with less than 

0.5 million barrels of oil equivalent total production were not 

included in any of the calculations in the methodology used 

for this assessment.

The following definitions are modified from Brennan and 

others (2010) and other sources indicated.

barrels of oil equivalent (BOE) A unit of petroleum volume in which the gas part is expressed in terms of its energy 

equivalent in barrels of oil. For this assessment, the energy 

equivalent (not the volume equivalent) of 6,000 cubic feet of 

natural gas equals 1 barrel of oil equivalent (Klett and others, 

2005).

buoyancy Upward force on one phase (for example, a fluid) 

produced by the surrounding fluid (for example, a liquid or a 

gas) in which it is fully or partially immersed, caused by differences in density.

buoyant trapping A trapping mechanism by which CO2 is 

held in place by a top and lateral seal (either a sealing formation or a sealing fault), creating a column of CO2

 in communication across pore space.

buoyant trapping pore volume (BPV) A geologically determined, probabilistic distribution of the volume fraction of the 

storage formation (SF) that can store CO2 by buoyant trapping. 

This distribution minimum is typically defined by existing plus 

forecast undiscovered oil and gas production volumes. The 

maximum is probabilistically calculated from distributions of 

geologic parameters describing the known trapping structures 

within the storage formation.

buoyant trapping storage efficiency (BSE) A distribution of 

efficiency values that describe the fraction of buoyant trapping 

that can occur within a volume of porous media. The values 

used in the methodology for this assessment (0.2 min, 0.3 

most likely, and 0.4 max) are discussed in Blondes, Brennan, 

and others (2013).

buoyant trapping storage resource (BSR) The mass of CO2

retained in the storage formation by buoyant trapping.

buoyant trapping storage volume (BSV) The volume of CO2

retained in the storage formation by buoyant trapping.

carbon sequestration Both natural and deliberate processes 

by which CO2 is either removed from the atmosphere or 

diverted from emission sources and stored in the ocean, terrestrial environments (vegetation, soils, and sediment), and 

subsurface geologic formations.

Federal lands One of five land-ownership categories used in 

this assessment for allocation of resources. Federal lands are 

lands within the United States owned or administered by the 

Federal Government. These include national parks, national 

wildlife refuges, military reservations, Federal prisons, and 

public-domain land. Spatial data for this category come from 

the State-specific spatial resources from the BLM available 
Glossary 9

National Oil and Gas Assessment (NOGA) U.S. Geological Survey National Oil and Gas Assessment, described 

at http://energy.usgs.gov/OilGas/AssessmentsData/

NationalOilGasAssessment.aspx.

offshore areas One of five land-ownership categories used 

in this assessment for allocation of resources. In this assessment, offshore areas refer to State waters (see definition). Both 

State and Federal offshore area boundaries are available from 

the National Atlas of the United States® at http://nationalatlas.

gov/mld/opdlm0p.html.

oil reservoir A subsurface accumulation of hydrocarbons 

composed primarily of oil that is contained in porous or fractured rock formations. An oil accumulation is defined by the 

USGS (Klett and others, 2005) as having a gas:oil ratio less 

than 20,000 cubic feet per barrel.

percentile In values sorted by increasing magnitude, any 

of the 99 dividers that produce exactly 100 groups with equal 

number of values (Everitt and Skrondal, 2010). The dividers 

are used to denote the proportion of values above and below 

them. The dividers are sequential integer numbers starting 

from the one between the two groups with the lowest values. 

For example, in the modeling of sequestration capacity, a 

95th percentile of 10 gigatons (Gt) denotes that 10 Gt divides 

all likely values into 95 percent of them below 10 Gt and 5 

percent above it.

permeability (k) A measure of the ability of a rock to permit 

fluids to be transmitted through it; it is controlled by pore size, 

pore throat geometry, and pore connectivity. Permeability is 

typically reported in darcies.

porosity (f ) The part of a rock that is occupied by voids or 

pores. Pores can be connected by passages called pore throats, 

which allow for fluid flow, or pores can be isolated and 

inaccessible to fluid flow. Porosity is typically reported as a 

volume, fraction, or percentage of the rock.

porosity of the net porous interval (fPI ) For this assessment, 

three values (minimum, most likely, and maximum) were 

estimated for the mean porosity of each net porous interval. 

The determination by the assessment geologist of how much 

porosity was sufficient to allow storage of CO2 was dependent 

on the geology of the storage formation, and this dependence 

did not allow for a fixed threshold.

pressure gradient The change in pore pressure per unit 

depth, typically in units of pound-force per square inch per 

foot (psi/ft), kilopascals per meter (kPa/m), or bars per meter 

(bar/m).

private and other lands One of five land-ownership categories used in this assessment for allocation of resources. Lands 

not owned by Federal, State, or Tribal entities are placed in 

this category of private and other lands. These lands either 

belong to private owners or, less commonly, belong to additional BLM-named ownership categories (such as county, city, 

water, and other) and are grouped together here. Spatial data 

for this category come from State-specific spatial resources 

from the BLM available at http://www.blm.gov; when data 

were not available from the BLM, they were obtained from 

individual State agencies.

residual trapping A mechanism by which CO2 is trapped 

as discrete droplets, blobs, or ganglia of CO2 as a nonwetting 

phase, essentially immiscible with the wetting fluid, within 

individual pores where the capillary forces overcome the 

buoyant forces.

residual trapping class 1 (R1) Storage formation rock with 

permeability greater than 1 darcy that is available for residual 

trapping.

residual trapping class 2 (R2) Storage formation rock with 

permeability ranging from 1 millidarcy to 1 darcy that is available for residual trapping.

residual trapping class 3 (R3) Storage formation rock 

with permeability less than 1 millidarcy that is available for 

residual trapping.

residual trapping pore volume (RPV) A calculated value equal 

to the storage formation pore volume (SFPV) minus the buoyant trapping pore volume (BPV). The value represents the pore 

volume within the storage formation that can be used to store 

CO2 by residual trapping; it is calculated during iterations of 

the Monte Carlo simulator after a value from the buoyant trapping pore volume distribution is randomly chosen by the simulator program (@RISK; version 5.7 is commercially available 

from Palisade Corporation: http://www.palisade.com/risk/). 

Calculations were made for the three residual trapping classes 

R1, R2, and R3 to obtain R1PV, R2PV, and R3PV.

residual trapping storage efficiency (RSE) A distribution of 

efficiency values that describes the fraction of residual trapping that can occur within a volume of porous media. The 

values used in the methodology for this assessment to define 

the distribution were calculated for each storage assessment 

unit by using equations from MacMinn and others (2010) and 

regional pressure and temperature data (Blondes, Brennan, and 

others, 2013). Calculations were made for the three residual 

trapping classes R1, R2, and R3 to obtain R1SE, R2SE, and R3SE.

residual trapping storage resource (RSR) The mass of CO2

retained in the storage formation by residual trapping. Calculations were made for the three residual trapping classes R1, R2, 

and R3 to obtain R1SR, R2SR, and R3SR.

residual trapping storage volume (RSV) The volume of CO2

retained in the storage formation by residual trapping. Calculations were made for the three residual trapping classes R1, R2, 

and R3 to obtain R1SV, R2SV, and R3SV.

seal A geologic feature that inhibits the mixing or migration 

of fluids and gases between adjacent geologic units. A seal is 

typically a rock unit or a fault; it can be a top seal, inhibiting 

upward flow of buoyant fluids, or a lateral seal, inhibiting the 

lateral flow of buoyant fluids.

seal formation The confining rock unit within the storage 

assessment unit. The seal formation is a rock unit that sufficiently overlies the storage formation and where managed 
10 National Assessment of Geologic Carbon Dioxide Storage Resources—Data

properly has a capillary entrance pressure low enough to effectively inhibit the upward buoyant flow of CO2

.

State lands One of five land-ownership categories used in 

this assessment for allocation of resources. This ownership 

category includes lands owned by State entities, as categorized 

by the BLM in State-specific land-ownership data obtained 

from http://www.blm.gov; when data were not available from 

the BLM, they were obtained from individual State agencies.

State waters State jurisdiction begins at the established 

baseline for the coast and extends 3 geographic (nautical) 

miles. However, there are special cases. Because of claims 

existing at the dates of statehood, Texas and the Gulf Coast of 

Florida have proprietary interest in a submerged belt of land, 

9 geographic miles wide, extending seaward along the coast 

(Thormahlen, 1999).

storage assessment unit (SAU) A mappable volume of rock 

that includes two main components: (1) the storage formation 

(SF), which is the reservoir for CO2 storage, and (2) a regional 

seal formation.

storage assessment unit code For each storage assessment 

unit, the nine-digit code identifies the USGS-specific storage 

assessment unit. The preceding letter “C” refers to a carbon 

dioxide storage assessment unit and distinguishes it from 

USGS National Oil and Gas Assessment (NOGA) Project 

assessment units that may have similar numbers. The first 

digit after “C” of the code denotes the world region number 

(5), the following three digits (034) denote the North America 

NOGA province number, the following two digits (C5034xx) 

denote the basin number (always 01 unless there is more than 

one basin in each province). The last two digits (C503401xx) 

denote the storage assessment unit number of that particular 

basin. In this report, the NOGA province and basin names are 

the same.

storage efficiency factor (BSE and RSE) Values representing the fraction of the total available pore space that will be 

occupied by free-phase CO2. Ranges of storage efficiency are 

specific to trapping types. The two used in this assessment 

were buoyant trapping storage efficiency (BSE) and residual 

trapping storage efficiency (RSE).

storage formation (SF) The reservoir of the storage assessment unit. The storage formation consists of sedimentary rock 

layers that are saturated with formation water having total 

dissolved solids (TDS) greater than 10,000 milligrams per 

liter (mg/L). In the CO2 assessment methodology, the storage 

formation resource calculation is the main resource calculation 

and consists of two parts: a buoyant trapping resource and a 

residual trapping resource.

storage formation pore volume (SFPV) The available pore 

space in the storage formation calculated from the area of 

the storage formation within the SAU and the thickness and 

porosity of the net porous interval. This value was used in the 

calculation of the residual trapping pore volume (RPV).

technically accessible storage resource (TASR) The mass 

of CO2 that may be injected and stored using present-day 

geologic and hydrologic knowledge of the subsurface and 

engineering practices. This term is analogous to the term 

“technically recoverable resource” used in USGS oil and gas 

assessments.

technically accessible storage volume (TASV) The volume 

of CO2 that may be injected and stored using present-day 

geologic and hydrologic knowledge of the subsurface and 

engineering practices.

thickness of the net porous interval (TPI) Defined in the 

methodology for this assessment as the mean net stratigraphic 

thickness of the portion of the storage formation that the 

assessment geologist determined contained an appropriate 

lithology with sufficient porosity to store CO2. Three values 

(minimum, most likely, and maximum) were estimated for the 

mean thickness of each net porous interval.

total dissolved solids (TDS) The quantity of dissolved material in a sample of water, usually expressed in milligrams per 

liter (mg/L).

trapping The physical and geochemical processes by which 

injected CO2 is retained in the subsurface.

Tribal lands One of five land-ownership categories used in 

this assessment for allocation of resources. Indian or Tribal 

lands within the United States are areas with boundaries 

established by treaty, statute, and (or) executive or court order, 

recognized by the Federal Government as territory in which 

American Indian Tribes have primary governmental authority. 

Spatial data for this category come from State-specific spatial 

resources from the BLM available at http://www.blm.gov and 

the National Atlas of the United States® at http://nationalatlas.

gov/mld/indlanp.html.
Tables 1 and 2

Tables 1 and 2 are in separate Excel files. Clicking on a table number below will link to the file.

Table 1. Comprehensive presentation of data used in the U.S. Geological Survey national 

assessment of geologic carbon dioxide storage resources.

Table 2. Correlation matrix for aggregation of data used in the U.S. Geological Survey national 

assessment of geologic carbon dioxide storage resources.
Appendix 1. Input Data Forms for 192 Storage 

Assessment Units Used in the U.S. Geological 

Survey National Assessment of Geologic 

Carbon Dioxide Storage Resources

The completed input data forms in appendix 1 are arranged alphabetically by basin name and 

then numerically by storage assessment unit (SAU) code. A complete list of basin names, SAU 

names, and SAU codes is in table 1. The first page of the input form contains identification 

information and the assessment geologist’s inputs; it has spaces for the assessment geologist’s 

name, the date of assessment, and the SAU location and its relation to NOGA assessment units 

(AUs), if appropriate, along with any notes from the assessor. In the input forms in appendix 1, 

no entries are shown for the last two categories because the information about the NOGA AUs 

was lengthy for some SAUs and because there were no significant notes from the assessors. 

Information on the related NOGA AUs is in table 1. The second page contains allocation percentages of the SAU mean area to the States that are listed alphabetically and of the SAU area to 

five general land-ownership categories that are defined in the “Glossary” in this report: Federal 

lands, State lands, Tribal lands, private and other lands, and offshore areas. More details about 

the forms are in the report text and figure 1.
Appendix 2. Empirical Cumulative Distribution 

Function Plots of Six Resource Types for Each 

of the 192 Storage Assessment Units Used in the 

U.S. Geological Survey National Assessment of 

Geologic Carbon Dioxide Storage Resources

The empirical cumulative distribution function (CDF) plots in appendix 2 are arranged alphabetically by basin name and then numerically by storage assessment unit (SAU) code. A complete 

list of basin names, SAU names, and SAU codes is in table 1. Each page in appendix 2 shows 

the probabilistic results of one quantitatively assessed SAU and contains six plots, one for each 

assessment output. These outputs are (1) the technically accessible storage resource (TASR); 

(2) the buoyant trapping storage resource (BSR); (3) the known recovery replacement storage 

resource (KRRSR); (4) the residual trapping class 1 storage resource (R1SR), for rocks with permeability greater than 1 darcy; (5) the residual trapping class 2 storage resource (R2SR), for rocks 

with permeability between 1 millidarcy (mD) and 1 darcy; and (6) the residual trapping class 3 

storage resource (R3SR), for rocks with permeability less than 1 mD. In each empirical CDF plot, 

the horizontal axis shows the storage resource (in millions of metric tons, Mt) and the vertical 

axis shows the cumulative probability between zero and one. The cumulative probability for a 

given percentile represents the probability that the true storage resource is less than the value 

shown. The points along the CDF are the mean and the P5, P50, and P95 percentiles as used in the 

rest of this report, although the labels on the plots lack subscripts and look like P5, P50, and P95. 

These values are also given in table 1. Output categories with a calculated storage resource of 

zero are labeled “No storage resource.” Where the mean and P50 values are the same within 

rounding to two significant figures, their respective dots on the curve may be slightly offset and 

reflect the unrounded values. All storage resource values greater than 1 Mt are rounded to two 

significant figures; all storage resource values less than 1 Mt are rounded to the nearest 0.1 Mt. 

For plots with storage resource values less than 1 Mt, a few points do not fall on the empirical CDF curve due to rounding error. All figures were created in R (R Core Team, 2013) using 

the ggplot2 package (Wickham, 2009). For more details on the calculations used to create the 

empirical CDF plots, see Brennan and others (2010) and Blondes, Brennan, and others (2013).
U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team—National Assessment—Data—Data Series 774, ver. 1.1